Abrasion resistant coating for stacks of fiber cement siding

ABSTRACT

This invention relates to a novel stack of siding, comprising: first and second coated siding pieces comprising an outer topcoat layer, an inner decorative coating layer and a fiberboard cement substrate layer; and a liner positioned between the first and second coated siding pieces. The siding, during normal transportation and installation, retains an acceptable appearance that is substantially free of viewable scratches or mars. In more preferred embodiments, the outer topcoat layer of the siding has a thickness of at least 8 microns and comprises a polyurethane dispersion. The present invention also provides novel methods of pre-finishing a fiberboard cement siding product, comprising the steps of: providing a fiberboard cement substrate layer; coating a first major surface of the fiberboard cement substrate with a decorative coating; coating the exposed surface of the decorative coating with a topcoat layer; and curing the topcoat layer to provide an abrasion resistant siding. More preferably, the curing step comprises a process that does not require heating the siding to a board surface temperature in excess of 100° C.

This application claims the benefit of U.S. Provisoinal Application Ser.No. 60/244,857, filed Nov. 11, 2000, which is incorporated herein byreference in its entirety.

BACKGROUND

Fiber cement composite siding is a relatively new and exciting buildingmaterial that was recently introduced to the United States marketplace.Siding made from fiber cement composite comprises a substrate made up ofwood pulp, silica and cement. One big advantage of this type of sidingis its great durability. Some manufacturers, in fact, warrantee thisproduct's continued function for up to fifty years. In comparison toshorter-lifetime vinyl or wood siding products this is a greatadvantage. Traditionally, fiber cement siding is often pre-painted (orpre-finished) in a factory setting and delivered to the job site, forexample, in stacks of 8 or 12-foot long sheets. The pre-painted sheets,which may be profiled to look like wood products, or scalloped or cut toresemble shingles, are ready for attachment to the building and yield aprimed and/or painted appearance immediately upon being so attached.

Unfortunately, however, fiber cement siding is a much heavier and a muchmore abrasive substrate compared to wood or vinyl siding products. Whilebuilders and homeowners desire the beauty and convenience of pre-paintedfiber cement boards, prefinished fiber cement siding products are oftenvisually marred or damaged, either during transit of the siding to thejob site or during installation. The damage is often caused as a resultof the heavy and abrasive pre-finished boards being rubbed against eachother. For example, during installation the quite abrasive bottomsurface of one piece of siding is able to easily mar the painted surfaceof another sheet. This can occur when a sheet being installed on a wallis slid against a sheet that already has been attached to the wall. Inanother situation the heavy sheets may rub against each other when theyare stacked or unstacked. It is quite common that some amount of slidingoccurs during these operations. In some cases the siding is packed in a“face-to-face” manner, though this is not always the case when thesiding profile does not lend itself to such stacking. Even in thesecases the heavy fiber cement siding is prone to visually apparent damagewhen the sheets are stacked or un-stacked, etc. While not intending tobe bound by theory, it is believed that small abrasive particles (e.g.,particles that come from the siding) can get between the faces ofadjacent sheets and act as abrasive grit against the pre-paintedsurface. In other cases, the faces of the siding are textured toresemble wood grain. This texture pattern is itself a somewhat roughsurface and face-to-face rubbing of the siding might cause abrasion ofthe pre-painted surfaces. Liners have been used to separate and protectthe sheets, however these liners often do not stay exactly between thesheets, thereby allowing an opportunity for the sheets to rub togetherand become damaged.

Clear coat systems have been used over wood or wood compositesubstrates.

These systems often are “bake finishes” that require heating to a boardsurface temperature above about 100° C., more typically above about 150°C. Unfortunately, fiber cement has very poor heat transfercharacteristics compared to traditional wood or wood composite sidingand would require long heat up and cooling times compared to traditionalsiding substrates. Many pre-finishing lines do not have the ovencapacity required to economically process such baked finishes.

From the foregoing, it will be appreciated that what is needed in theart is a pre-finished fiberboard siding product that maintains itsfactory appearance during transit and normal handling. Such sidingproducts and methods for preparing the same are disclosed and claimedherein.

SUMMARY

In one embodiment, this invention relates to a novel stack of siding,comprising: first and second coated siding pieces comprising an outertopcoat layer, an inner decorative coating layer and a fiberboard cementsubstrate layer; and a liner positioned between the first and secondcoated siding pieces. In preferred embodiments, the siding, duringnormal transportation and installation, retains an acceptable appearancethat is substantially free of viewable scratches or mars. In morepreferred embodiments, the fiberboard cement substrate layer compriseswood pulp, silica and cement and has a density of at least 1 g/cm³. Alsoin more preferred embodiments, the outer topcoat layer of the siding hasa thickness of at least 8 microns and comprises a coating selected fromthe group consisting of polyurethane dispersions, acrylic emulsions,waterborne multi-component urethanes, waterborne multi-componentepoxies, UV cured acrylics, visible light cured acrylics, and acrylicwaterborne fluoropolymers. In most preferred embodiments, the outertopcoat layer comprises a polyurethane dispersion, wherein the outertopcoat layer is cured at a board surface temperature less than 100° C.

The present invention also provides novel methods of pre-finishing afiberboard cement siding product, comprising the steps of: providing afiberboard cement substrate layer; coating a first major surface of thefiberboard cement substrate with a decorative coating; coating theexposed surface of the decorative coating with a topcoat layer; andcuring the topcoat layer to provide an abrasion resistant siding. Morepreferably, the curing step comprises a process that does not requireheating the siding to a board surface temperature in excess of 100° C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 illustrate alternative exploded cross-sections of a partialstack of fiber cement siding of the present invention.

DETAILED DESCRIPTION

The present invention provides a mar and abrasion resistant pre-painted(or pre-finished) fiber cement siding products. Surprisingly, it hasbeen discovered that by applying a clear topcoat finish (e.g., a lowtemperature cured topcoat) over a pre-painted or pre-finished fibercement product, dramatically improves the mar and abrasion resistance ofthe product. The preferred low temperature cure topcoat finishes of thepresent invention provide a practical way for pre-finishers to furtherprotect the painted surface on fiber cement substrates without the useof high temperature ovens.

By “mar and abrasion resistant” is meant that the overall productretains an acceptable appearance during transit and normal handling. Thetopcoat of the present invention may itself, in certain circumstances,become somewhat scratched or marred after transit and normal handling.Surprisingly, however, scratches and mars that are confined within thistopcoat layer do not undesirably impact the visual appearance of theoverall product.

As used herein, the terms “siding,” “stacks of siding” or “sidingproducts” are meant to include both siding products and trim products.

The current method of providing a pre-finished fiberboard cement product(i.e., where the product is finished prior to delivery and installationat the building site) requires elaborate packaging and handling methodsto prevent damage of the pre-painted or pre-finished product.Unfortunately, these measures are only marginally effective inpreventing damage and the product often must be repainted afterinstallation. This invention preferably will protect the appearance offiber cement products during the stacking, shipping, and installationprocesses. The result is less visual coating damage and, consequently,less need for touch-up repairs after installation.

Suitable fiber cement substrates for use in the present inventioninclude composites of wood pulp (e.g., comprising cellulosic fibers),silica and cement (e.g., portland cement). A variety of such fibercement products are now available on the market. For example, a premiumfiber cement siding product is available from James Hardie BuildingProducts Inc. These premium products (which include HARDIPLANK lapsiding, HARDIPANEL vertical siding, HARDISHINGLESIDE, and HARDIEHOMEsiding) are said to offer the warmth of wood, and the durability offiber-cement. These products offer a 50-year transferable warranty, andare said to resist moisture damage, be low maintenance, not crack, rotor delaminate, resist damage from extended exposure to humidity, rain,snow, salt air and termites, and be non-combustible. Other suitablefiber cement siding products include CEMPLANK and CERTAINTEED.

Typical fiber cement substrates are quite heavy and have a density ofbetween about 1 and 1.6 g/cm³ or even higher.

Suitable fiber cement substrates for use in the present inventioninclude unprimed fiber cement substrates that are decorated and topcoated as described herein and commercially available pre-primed orpre-painted fiber cement substrates that are top coated as describedherein.

The improved siding of the present invention comprises one or morelayers of a decorative coating. For example, in one preferred embodimentthe decorative coating comprises a primer layer and one or more coloredlayers. An optional sealer layer underneath the primer layer may also beutilized, if desired. The choice of particular sealer, primer andcolored layer is not critical. However, the layers underneath thetopcoat and the particular topcoat selected should be preferablyselected such that there is adequate adhesion of the topcoat to theunderlying layer(s).

Suitable optional sealer layers include acrylic latex materials. Ingeneral, the typical function of a sealer layer is to provide one ormore feature such as efflorescence blocking, water resistance and/orblock resistance. An example of a commercially available sealer isOLYMPIC FC sealer (available from PPG).

Suitable optional primer layers include acrylic latex or vinyl primers.The primer may comprise color pigments, if desired.

Suitable decorative coatings include acrylic latex paints andcommercially available coatings such as VALPRO FC (available from TheValspar Corporation), OLYMPIC FC (available from PPG) and 1500 SeriesCabot Factory Finish and C³ Factory Finish (both available from CabotCorporation). These coatings are in some respects similar to standardexterior house paints; however, they have been formulated to work oncement substrates and in a factory finish application.

It has been discovered that applying a low temperature cure topcoat(preferably having a dry thickness of, for example, as low as about 5microns, preferably at least 7 microns, more preferably at least 8microns, and most preferably at least 10 microns) to a painted orfinished fiber cement substrate provides a protective (or in someinstances sacrificial) layer that imparts a significant improvement inmar (e.g., scratch) and abrasion resistance to the overall siding. Inpreferred embodiment the topcoat comprises a low temperature curedwaterborne finish.

Suitable topcoats include polyurethane dispersions (PUDs), acrylicemulsions, waterborne multi-component urethanes, waterbornemulti-component epoxies, UV or visible light cured acrylics, acrylicwaterborne fluoropolymers, etc. Solvent borne systems may also be used,though they are not preferred for environmental reasons.

The presently preferred topcoat for use in the present inventioncomprises a polyurethane dispersion. Suitable polyurethane dispersionsfor use in the present invention include those described, for example,in U.S. Pat. Nos. 3,412,054; 4,664,030; 4,983,662; 5,147,925; 5,541,251;5,571,861; 5,637,639; 5,710,209; 5,854,332; 5,872,182; 6,031,041; and6,063,861 and in WO 00/24837. Other suitable polyurethane dispersionsfor use in the present invention include those described, for example,in Self-crosslinkable Urethanes and Urethane/Acrylates, VerfkroniekNummer 1 Jan. 1999 and in New Polymer Synthesis for (self) CrosslinkableUrethanes and Urethane Acrylics, 4^(th) Nurnberg Congress, Paper 17 byTennebroek, Geurts, Overbeek and Harmsen.

Commercially available polyurethane dispersions that may be used informulating topcoats of the present invention include, for example, EPS4203 (available from Engineered Polymer Solutions, Inc.) and NEORZ R9637(available from Zenaca). Commercially available acrylics that may beused in formulating topcoats of the present invention include, forexample, EPS 2718 (available from Engineered Polymer Solutions, Inc.).Other suitable commercially available resins for use in preparingtopcoats of the present invention include AZORES acrylic waterbornefluoropolymer (available from The Valspar Corporation).

Polyurethane dispersions generally comprise a polymer formed from apolyisocyanate, a polyol, and a carrier (e.g., water and/or othersolvents). There is a large freedom of choice in selecting theparticular polyisocyanate, polyol or carrier. Suitable polyisocyanatesinclude aliphatic isocyanates and aromatic isocyanates. Aliphaticisocyanate based PUDs are presently preferred.

Examples of some suitable isocyanates for use in the present inventioninclude hexamethylene diisocyanate (HDI), isophorone diisocyanate(IPDI), 4,4′-methylene-dicyclohexylisocyanate (H₁₂MDI), tolueneisocyanate (TDI), 4,4′-methylene-diphenylisocyanate(MDI), etc.

Examples of some suitable polyols for use in the present inventioninclude polyether polyols, polyester polyols, polyamide polyols,polycarbonate polyols, etc.

If desired the polyurethane dispersion or the topcoat formulation maycomprise a dispersing compound (e.g., a hydroxy alkanoic acid) and/or achain extender (e.g., a diamine). Suitable chain extenders include, forexample, hydrazine, ethylene diamine, butane diamine, hexane diamine,isophorone diamine, etc.

The polyurethane dispersions of the present invention preferably have anumber average molecular weight of at least 1,800, more preferably atleast 5,000, and most preferably at least 9,000. For urethane/acrylatesthe Mn ranges specified above optimally apply to both the urethanepolymer component and the acrylic polymer component. The polyurethanedispersions of the present invention preferably have an acid number ofbetween 6.5 and 80, more preferably between 9 and 50, and mostpreferably between 10 and 30 (where acid number is expressed in mg KOHper gram of solid polymer).

As previously mentioned, the topcoats of the present invention arepreferably hardened without the need to heat the substrate surface to ahigh temperature. Consequently, radiation hardened systems (e.g., UV orvisible-light cured systems) may be used. Alternatively, multi-componentsystems (e.g., two-part systems) may be employed. Multi-componentsystems may be hardened, for example, by mixing the components prior toor during application to the substrate and allowing the mixed componentsto harden on the substrate. Other low temperature cured systems may beutilized.

The topcoat may be applied to the pre-painted or pre-finished substrateusing any suitable application method. For example, the topcoat may beroll coated, sprayed, curtain coated, vacuum coated, brushed, or floodcoated using an air knife system. Preferred application methods providea uniform coating thickness and are cost efficient.

The topcoat layer preferably is clear or only lightly pigmented.Generally, the topcoats of the present invention have a PVC (pigmentvolume concentration) of less than 20 percent, more preferably less than15 percent.

It has been found that the thickness of the topcoat layer can affect theperformance of the present invention. For example, if the topcoat is toothin the siding may not achieve the desired amount of mar and abrasionresistance. If the topcoat is too thick the costs of the system willunnecessarily increase or the color of the decorative layer may becompromised (e.g., the product may appear hazy or cloudy). A suitablethickness for the topcoat layer is between 5 and 100 microns, preferablybetween 7 and 50 microns, more preferably between 8 and 30 microns, andmost preferably between 10 and 25 microns.

The topcoat may be cured using any suitable process (e.g., two-partcuring mechanism, radiation curing, air drying, heat curing, etc.). Morepreferably, the topcoat is cured without the need to heat the cementsubstrate to a high temperature. Although heat curing is within thescope of the present invention, it is somewhat less efficient forcement-based products given their low heat transfer characteristics.Consequently, preferred processes generally require board surfacetemperatures of less than 100° C., more preferably less than 80° C., andmost preferably less than 70° C.

The topcoat may further comprise abrasion resistance promoting adjuvantssuch as silica or aluminum oxide.

A presently preferred formula for a suitable topcoat of the presentinvention (Formula A) is made according to the following procedure. In ahigh-speed mixer is charged 594 parts EPS 4203 PUD (available fromEngineered Polymer Systems, Inc.). To this is added AMP-95 (2 parts,2-amino 2-methyl 1-propanol, available from Angus Chemical) with goodagitation. Water (50 parts), NOPCOSPERSE 44 (20 parts, available fromHenkel), TS-100 silica (63 parts, available from Degussa) and water (110parts) are pre-mixed with a high-speed mixer and added to theaforementioned EPS 4230 and AMP-95 mixture. DOWANOL DPNB (15 parts,available from Dow) and water (15 parts) are pre-mixed and added to theabove. To this is then added KATHON LX 1.5 PCT preservative (1 part,available from Rohm & Haas) and POLYPHASE AF-1 anti-microbial agent (3parts, available from Troy Chemical). The total mixture is then mixed athigh speed for ten minutes and held at a temperature of about 27° C. Agrind test may be run, if desired. Typically, the formulation at thisstage will have about a 6+ HEGMAN value. To the above is added 20 partswater and BYK-025 defoamer (1.2 parts, available from BYK).

An alternative preferred formula for a suitable topcoat of the presentinvention (Formula B) is made according to the following procedure. In ahigh-speed dispersion tank is charged 189.5 parts water. To this isadded under agitation TAMOL 731 surfactant (20 parts, available fromRohm & Haas), AMP-95 (2 parts, 2-amino 2-methyl 1-propanol, availablefrom Angus Chemical), DOWANOL DPNB co-solvent (23 parts, available fromDow Chemical), BYK-025 defoamer (1.2 parts available from BYK), KATHONLX 1.5% preservative (1 part, available from Rohm & Haas), BUSAN 1292anti-microbial agent (2 parts, available from Buckman) and EPS 4203 PUD(420 parts, available from Engineered Polymer Systems, Inc.). To this isadded TS-100 silica (50 parts, available from Degussa) slowly under highagitation. The mixture is dispersed for approximately 15 minutes to a 4Hegman and held at 21 to 32° C. To this is added additional EPS 4203 PUD(173 parts) and water (1 part). Typically, the mixture will have aviscosity of about 17 to 20 seconds (using a Zahn #3 EZ Viscosity Cup(available from Paul N. Gardner Co.). If desired an optional thickeningagent may be utilized to achieve this viscosity.

Stacks of the siding of the present invention are often assembled usinga liner between adjacent sheets of the siding. Suitable liners includesheet and film materials that can help protect the siding from damagewhen adjacent sheets are rubbed together. The liners may, if desired,adhere lightly to the siding (thereby helping keep the liner against themajor surface of the siding) or simply remain in place by friction.

Suitable liners include paper, plastic, foam, non-woven or fabric sheetor film materials. Preferred liners include foam sheets, e.g.,polyethylene foam sheets having a thickness sufficient to cushion thesheets to thereby further protect the siding. An example of suitablesuch foam sheets include sheets having a thickness of between about 0.15to 0.6 cm.

The stacks of siding may be assembled in a face-to-face pattern (i.e.,pairs of siding are stacked with each pair having the decorative majorsurfaces adjacent each other) or in a face-to-back pattern (i.e., thestack comprises two or more pieces of siding with the siding stacked inone orientation).

FIG. 1 illustrates an exploded cross-section of a partial stack 10 offiber cement siding of the present invention. As illustrated, two piecesof siding (34 and 32) are shown one on top of the other (in aface-to-back orientation), with a liner 30 interposed there between. Itis understood that in normal use siding piece 34 would directly contactliner 30 which would directly contact siding piece 32. Siding pieces 34and 32 each have a viewable surface 20 and an abrasive surface 28. Thesiding pieces 34 and 32 are illustrated having three basic layers (22,24, 26). It is understood that additional layers or sub-layers may beadded without departing from the scope or spirit of this invention.Layer 22 illustrates a protective topcoat layer. Preferably layer 22comprises a clear layer having a thickness of between 10 and 20 microns.Layer 24 illustrates a decorative layer. Typically, this decorativelayer will comprise a colored paint material. Layer 26 illustrates thefiberboard cement substrate. Layer 26 is illustrated with a majorabrasive surface 28. If desired, stack 10 could be alternativelyassembled in a face-to-face orientation (i.e., piece 34 could be flippedupside down and layer 22 of piece 34 could be adjacent liner 30).

FIG. 2 illustrates an alternative exploded cross-section of a partialstack 12 of fiber cement siding of the present invention. Asillustrated, two pieces of siding (34 and 32) are shown one on top ofthe other, with a liner 30 interposed there between. Siding pieces 34and 32 each have a viewable surface 20 and an abrasive surface 28. Thesiding pieces 34 and 32 are illustrated having three basic layers (22,24, 26). However, in this embodiment layer 22 illustrates a protectivelayer on the bottom of the siding piece. Preferably layer 22 comprises alayer having a thickness sufficient to smooth the normally rough andabrasive surface of the fiber cement, thereby providing a relativelysmooth (or at least not as abrasive) surface 29. Layer 24 illustrates adecorative layer. Typically, this decorative layer will comprise acolored paint material. Layer 26 illustrates the fiberboard cementsubstrate.

FIG. 3 illustrates an alternative exploded cross-section of a partialstack 14 of fiber cement siding of the present invention. Thisembodiment is quite similar to that shown in FIG. 1 and illustrates thatthe siding of the present invention may have more than one layer of adecorative coating. In this embodiment, layer 25 comprises a primercoating that is applied between the decorative layer 24 and the fibercement substrate 26. If desired, stack 14 could be alternativelyassembled in a face-to-face orientation (i.e., piece 34 could be flippedupside down and layer 22 of piece 34 could be adjacent liner 30).

The following examples are offered to aid in understanding of thepresent invention and are not to be construed as limiting the scopethereof. Unless otherwise indicated, all parts and percentages are byweight. The constructions cited were evaluated by tests as follows:

Visual Assessment of Mar and Abrasion Resistance:

Preferred topcoats provide mar and abrasion resistance to the overallfiber cement product. The mar and abrasion resistance may be visuallyassessed by performing a steel wool rub test. Preferred topcoats provideresistance even when rubbed, as described herein, for 20 double rubsusing a back and forth motion and a medium coarse #2 steel wool pad(available from Rhodes American). The rubbed samples are then cleanedwith water, allowed to dry, and visually assessed using a ten-pointscale as described on the following table. Rating value Appearance ofthe panel  0 Unacceptable appearance - severe loss of gloss and coatingwhere rubbed. 1-3 Unacceptable appearance - severe loss of gloss andsome loss of coating. 4-6 Acceptable appearance - slight change inappearance, e.g., some decrease in gloss and minor loss of coating. 7-9Acceptable appearance - minor change in appearance, e.g., some minordecrease in gloss and minor loss of coating. 10 Acceptable appearance -negligible change in appearanceAn average rating for three tests is recorded.

EXAMPLES Example 1 Low Temperature Cure PUD

The clear topcoat of Formula A was spray applied to 15 cm by 20 cmpieces of pre-finished fiber cement siding panel (Cedar Mill SelectHARDIPLANK lap siding having VALPRO Factory Finish, available from JamesHardie Building Products Inc.) at varying thickness. The topcoat coatedpieces were then processed through a 150° C. oven to a board surfacetemperature of 60° C. (as measured using an infrared pyrometer).

After being conditioned to room temperature, the pieces were tested asdescribed above for mar and abrasion resistance. The results for threesamples at each thickness were: Thickness of dried topcoat (microns)Assessment rating  0 (control without topcoat) 0  5 2  8 4 14 6 18 7 227 36 8

The above data illustrates that fiber cement products having a topcoatsystem of the present invention provide significant mar and abrasionresistance compared to fiber cement products that do not incorporate theimproved topcoat system.

Example 2 Low Temperature Cure PUD

The clear topcoat of Formula B was spray applied to 15 cm by 20 cmpieces of pre-finished fiber cement siding panel (Cedar Mill SelectHARDIPLANK lap siding having VALPRO Factory Finish, available from JamesHardie Building Products Inc.) at varying thickness. The topcoat coatedpieces were then processed through a 150° C. oven to a board surfacetemperature of 60° C. (as measured using an infrared pyrometer).

After being conditioned to room temperature, the pieces were tested asdescribed above for mar and abrasion resistance. The results for threesamples at each thickness were: Thickness of dried topcoat (microns)Assessment rating  0 (control without topcoat) 0  5 2  8 2 14 5 18 7 227 36 9

The above data illustrates that fiber cement products having a topcoatsystem of the present invention provide significant mar and abrasionresistance compared to fiber cement products that do not incorporate theimproved topcoat system.

Having thus described the preferred embodiments of the presentinvention, those of skill in the art will readily appreciate that theteachings found herein may be applied to yet other embodiments withinthe scope of the claims hereto attached. The complete disclosure of allpatents, patent documents, and publications are incorporated herein byreference as if individually incorporated.

1. A stack of siding, comprising: a first coated siding piece comprisingan outer topcoat layer, an inner decorative coating layer and afiberboard cement substrate layer; a second coated siding piececomprising an outer topcoat layer, an inner decorative coating layer anda fiberboard cement substrate layer; and a liner positioned between thefirst coated siding piece and the second coated siding piece.
 2. Thestack of siding of claim 1, wherein during normal transportation andinstallation of the siding the siding retains an acceptable appearancethat is substantially free of viewable scratches or mars.
 3. The stackof siding of claim 1, wherein the siding is stacked in a face-to-facepattern.
 4. The stack of siding of claim 1, wherein the siding isstacked in a face-to-back pattern.
 5. The stack of siding of claim 1,wherein the fiberboard cement substrate layer comprises wood pulp,silica and cement.
 6. The stack of siding of claim 1, wherein thefiberboard cement substrate layer has a density of at least 1 g/cm³. 7.The stack of siding of claim 1, wherein the outer topcoat layer has athickness of at least 8 microns.
 8. The stack of siding of claim 1,wherein the outer topcoat layer has a thickness of at least 10 microns.9. The stack of siding of claim 1, wherein the outer topcoat layercomprises a coating selected from the group consisting of polyurethanedispersions, acrylic emulsions, waterborne multi-component urethanes,waterborne multi-component epoxies, UV cured acrylics, visible lightcured acrylics, and acrylic waterborne fluoropolymers.
 10. The stack ofsiding of claim 1, wherein the outer topcoat layer comprises apolyurethane dispersion.
 11. The stack of siding of claim 1, wherein theouter topcoat layer is cured by a process selected from the groupconsisting of: two-part curing mechanism, radiation curing, air dryingand heat curing.
 12. The stack of siding of claim 1, wherein the outertopcoat layer is cured at a board surface temperature less than 100° C.13. The stack of siding of claim 1, wherein the outer topcoat layer iscured at a board surface temperature less than 80° C.
 14. The stack ofsiding of claim 1, wherein the liner comprises a foam sheet.
 15. Thestack of siding of claim 1, wherein the siding piece exhibits at most aslight change in appearance after 20 double rubs with medium coarse #2steel wool pad.
 16. The stack of siding of claim 1, wherein the sidingpiece exhibits at most a minor change in appearance after 20 double rubswith medium coarse #2 steel wool pad.
 17. A method of making afiberboard cement siding product, comprising the steps of: providing afiberboard cement substrate layer; coating a first major surface of thefiberboard cement substrate with a decorative coating; coating theexposed surface of the decorative coating with a topcoat layer; andcuring the topcoat layer to provide a mar and abrasion resistant siding.18. The method of claim 17, wherein the curing step comprises a processthat does not expose the siding to a board surface temperature in excessof 100° C.
 19. The method of claim 17, wherein the fiberboard cementsubstrate layer has a density of at least 1 g/cm³ and comprises woodpulp, silica and cement, the outer topcoat layer comprises apolyurethane dispersion and has a thickness of at least 8 microns. 20.The method of claim 17, wherein the finished siding piece exhibits atmost a slight change in appearance after 20 double rubs with mediumcoarse #2 steel wool pad.
 21. A stack of siding, comprising: a firstcoated siding piece comprising an outer topcoat layer having a thicknessof at least 8 microns, an inner decorative coating layer and afiberboard cement substrate layer; and a second coated siding piececomprising an outer topcoat layer having a thickness of at least 8microns, an inner decorative coating layer and a fiberboard cementsubstrate layer; wherein each outer topcoat layer is prepared from apolyurethane dispersion cured at a temperature that does not expose thesiding to a board surface temperature in excess of 100° C.
 22. The stackof siding of claim 21, wherein the fiberboard cement substrate layercomprises wood pulp, silica and cement.
 23. The stack of siding of claim21, wherein the fiberboard cement substrate layer has a density of atleast 1 g/cm³.
 24. The stack of siding of claim 21, wherein the outertopcoat layer has a thickness of at least 10 microns.
 25. The stack ofsiding of claim 21, wherein the outer topcoat layer is cured at a boardsurface temperature less than 80° C.
 26. The stack of siding of claim21, further comprising a liner positioned between the first coatedsiding piece and the second coated siding piece.
 27. The stack of sidingof claim 26, wherein the liner comprises a foam sheet.
 28. The stack ofsiding of claim 21, wherein the siding piece exhibits at most a slightchange in appearance after 20 double rubs with medium coarse #2 steelwool pad.
 29. A method of making a fiberboard cement siding productprior to attaching the product to a building, the method comprising:providing a fiberboard cement substrate; coating a first major surfaceof the fiberboard cement substrate with a decorative coating; coatingthe exposed surface of the decorative coating with a topcoat layercomprising a polyurethane dispersion; and curing the topcoat layer toprovide a mar and abrasion resistant coated fiberboard cement sidingproduct; wherein curing comprises a thermal curing process that does notexpose the siding to a board surface temperature in excess of 100° C.;wherein the fiberboard cement substrate has a density of at least 1g/cm³ and comprises wood pulp, silica and cement, and the outer topcoatlayer has a dry thickness of at least 8 microns.
 30. The method of claim29, wherein the finished siding piece exhibits at most a slight changein appearance after 20 double rubs with medium coarse #2 steel wool pad.31. The method of claim 29, wherein prior to coating a first majorsurface of the fiberboard cement substrate with a decorative coating,the first major surface is coated with a sealer and/or a primer.
 32. Themethod of claim 29, wherein the topcoat layer further comprises anabrasion resistance promoting adjuvant.
 33. The method of claim 29,further comprising stacking a first coated fiberboard cement sidingproduct against a second coated fiberboard cement siding product.
 34. Amethod of making a stack of fiberboard cement siding products,comprising: preparing two or more coated fiberboard cement sidingproducts, the method comprising: providing a fiberboard cementsubstrate; optionally coating a first major surface of the fiberboardcement substrate with one or more layers comprising a sealer, a primer,or both; coating one or more layers of a decorative coating to theoutermost surface of the optionally coated fiberboard cement substrate;coating the exposed surface of the one or more layers of a decorativecoating with a topcoat layer comprising a polyurethane dispersion;curing the topcoat layer to provide a mar and abrasion resistant coatedfiberboard cement siding product; wherein the curing step comprises athermal curing process that does not expose the siding to a boardsurface temperature in excess of 100° C.; and stacking the two or morecoated fiberboard cement siding products to form a stack; wherein thefiberboard cement substrate has a density of at least 1 g/cm³ andcomprises wood pulp, silica and cement, and the outer topcoat layer hasa dry thickness of between 8 and 100 microns.
 35. The method of claim34, wherein the polyurethane dispersion is an aliphatic isocyanate-basedpolyurethane dispersion.
 36. The method of claim 34, wherein thepolyurethane dispersion comprises a polyurethane having a number averagemolecular weight of at least
 1800. 37. The method of claim 34, whereinthe polyurethane dispersion comprises a polyurethane having an acidnumber between 6.5 and 80 mg KOH per gram solid polymer.
 38. The methodof claim 34, wherein the topcoat layer has a pigment volumeconcentration of less than 20 percent.
 39. The method of claim 34,wherein the outer topcoat layer has a dry thickness of at least 10microns.
 40. The method of claim 34, wherein the thermal curing processprovides a board surface temperature of less than 80° C.